The invention relates to a displacement type rotary air induction-and-blower machine.
Machines of the type in question, known as side channel machines, substantially comprise a vaned impeller accommodated internally of a casing that consists in a first and a second half-shell paired together in such a way as to create an annular channel, that is, the side channel from which the machine takes its name, and internally of which the vanes of the impeller rotate. The two ends of the annular channel afford an inlet port and an outlet port through which fluid is drawn into and expelled from the machine, respectively. In most instances, the inlet and outlet ports are formed in the first half-shell, to which the impeller drive motor is also connected, whilst the second half-shell serves simply as a cover, and as a means of encasing a part of the annular channel.
It is common practice to connect two such machines in series so as to form a two-stage unit. In such a situation, the casing which contains the impellers will comprise not only two outer half-shells, but also an intermediate half-shell that separates the two stages.
Conventionally, the two-stage unit utilizes two half-shells of special shape, incorporating ducts that connect the outlet of the first stage with the inlet of the second stage; besides creating certain leakage problems connected with the passage of the fluid through the ducts, such an arrangement brings the additional drawback that to enable construction of both single- and two-stage machines, a number of different molds are required, signifying increased manufacturing and stock-related costs.
A second type of arrangement consists in cascading two standard single-stage units in direct fashion, rotating the casings through a given angle about the axes of their impellers in such a way that the inlet of the second stage can be offered to the outlet of the first stage; while simple enough in principle, such an arrangement is beset nonetheless by the serious drawback that two sharp changes in direction (each of 90.degree.) are imposed on the fluid, the result of which is a heavy loss of efficiency in the combined two-stage unit.
Accordingly, the object of the present invention is one of overcoming the drawbacks described above by providing a machine that can be embodied in both single stage and two-stage versions utilizing the same casing components, subject to a minimum of modification obtainable through simple machining operations, and which, in the two-stage version, enables a limitation of the length and tortuousness of the path followed by the fluid exiting from the first stage and entering the second.